The Lowther website writes about a Hi-Ferric technology in its DX series. Interesting mechanism of action. A rear-view picture of a DX driver did not show independent connections to "field coils"; as reminescent of ancient drivers. It has a magnet, and only the usual two connections to a power amp. The peak excursion of the diaphragm was quoted at 2 millimeters peak to peak. Prices [in Pounds Sterling] appeared reasonable in the range for~280-550. However; no impedance versus frequency plot was shown for any one driver.

Mr. Pass: The Rothacher SIT amp Version 2 used an inductance as a load to the SIT. I have [mentally] replaced Rothacher's coil with the Field Coil of the Lowther you'll be using for BAF 2012. The attached file [lowthersit.pdf] shows a proposed schematic whereby a SIT [or other FET] simultaneously drives the Field and the Voice Coils of this loudspeaker. This is a new situation of a fixed plus a signal modulated loudspeaker magnetic field. By comparison, Lowther-America recommends using a clean DC power supply to generate a fixed magnetic field.

somehow I have impression that both Lowther and your ears wouldn't be happy with that solution

in dark ages , FC of speaker was used as choke in PS , for tooboolar amps ; and even then,when Movie Theater was crowded , demanding more A2 from flea powerful amps ..... entire first row of spectators wasn't entirely happy .......

then they invented pentodes and PP , screaming how there is free lunch , at last

somehow I have impression that both Lowther and your ears wouldn't be happy with that solution

in dark ages , FC of speaker was used as choke in PS , for tooboolar amps ; and even then,when Movie Theater was crowded , demanding more A2 from flea powerful amps ..... entire first row of spectators wasn't entirely happy .......

then they invented pentodes and PP , screaming how there is free lunch , at last

intention of revived (not just nowadays) using of FC in speaker construction is impeccable constant magnetic flux , not influenced with constant variable EMF made by vibrating voice coil

sort of idea that FC is having much lesser "intrinsic impedance " than any permanent magnet

even if you embrace idea of using FC as (even just partial ) choke load for amp , connected to counteract non-linear distortion in rest of speaker/amp combo , I resume that having any success demands sooooooooo complicated and loooong process